10 CONTROL OPERATION
The Liebert® MC Premium Efficiency Control takes about 30 seconds to boot during which time, the LED on the Premium
Efficiency Control Board reads “888.” When fully booted, “F00” displays, then the value for F00. When using the control, the
condenser fan(s) respond less than five seconds after receiving a "compressor-on" signal from the indoor unit. Consider using
UPS equipment on both data center cooling units and Liebert® MC condensers to maintain uninterrupted cooling
capability.
For the first 60 seconds of operation after the compressor turns on, the condenser fan(s) run at a factory set fixed speed,
based on ambient temperature: faster at higher temperatures, slower at lower temperatures. After 60 seconds, the control
adjusts the fan speed based on the liquid pressure transducer. If the liquid pressure transducer fails, the condenser uses
temperature sensors to control the fan speed based on the liquid line temperature. The condenser fans continue to operate
for approximately 30 seconds after compressors turn Off.
The MC fans have various alarm conditions, such as loss of voltage and loss of control signal, that stop the condenser fans.
When an alarm condition is no longer present the fans turn on automatically if compressors are On.
10.1 Premium Efficiency Control Board and Interface
The Premium Efficiency Control board has a stacked board arrangement. The human machine interface consists of three,
7-segment LEDs and keys (see Figure 10.2 on the next page).
NOTE: Indicator lights should be On to indicate signal is present. See Figure 10.1 on the next page.
The Premium Efficiency Controls are factory configured for refrigerant type, whether or not a receiver is included, and the
indoor cooling unit. No field configuration is necessary for proper and efficient condenser operation.
10 Control Operation
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Summary of Contents for Liebert MC series
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